﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.SharePoint;

namespace de.rwth.rz.campus.sputils.Security
{
    /// <remarks>
    /// 
    /// Copyright 2010 RWTH Aachen, CAMPUS Labs
    /// 
    /// Licensed under the Apache License, Version 2.0 (the "License");
    /// you may not use this file except in compliance with the License.
    /// You may obtain a copy of the License at
    ///
    /// http://www.apache.org/licenses/LICENSE-2.0
    ///
    /// Unless required by applicable law or agreed to in writing, software
    /// distributed under the License is distributed on an "AS IS" BASIS,
    /// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    /// See the License for the specific language governing permissions and
    /// limitations under the License.
    /// 
    /// This class can be used to send emails to SharePoint groups.
    /// For every SharePoint user in a SharePoint group an email is generated.
    /// Be aware of the load of your SMTP server.
    /// 
    /// </remarks>
    public class SPSiteSecurity
    {
        /// <summary>Returns an elevated siteCollection</summary>
        /// <param name="siteCollection">
        /// The siteCollection that you want an elevated instance of.
        /// You must dispose of this object unless it is part of SPContext.Current.
        /// </param>
        /// <returns>An elevated siteCollection context.</returns>
        /// <remarks>Be sure to dispose of objects created from this method.</remarks>
        public static SPSite GetElevatedSite(SPSite siteCollection)
        {
            var sysToken = GetSystemToken(siteCollection);
            return new SPSite(siteCollection.ID, sysToken);
        }

        /// <summary>Gets a UserToken for the system account.</summary>
        /// <param name="siteCollection"></param>
        /// <returns>A usertoken for the system account user./returns>
        /// <remarks>Use this token to impersonate the system account</remarks>
        private static SPUserToken GetSystemToken(SPSite siteCollection)
        {
            siteCollection.CatchAccessDeniedException = false;
            try
            {
                return siteCollection.SystemAccount.UserToken;
            }
            catch (UnauthorizedAccessException)
            {
                SPUserToken sysToken = null;

                //Use RunWithElevatedPrivileges to grab the system user token.
                SPSecurity.RunWithElevatedPrivileges(
                    delegate()
                    {
                        using (SPSite tmpSite = new SPSite(siteCollection.ID))
                        {
                            sysToken = tmpSite.SystemAccount.UserToken;
                        }
                    }
                );
                return sysToken;
            }
        }
    }
}
